Something for you
"If you want cook with this rom please following:
step 1. use ezxcodec or sbf extract. to decompose this rom, and rename the CG33.smg as os.nb. this os.nb which we can cook with.
step 2. use imgfstools to dump it and to merge it
imgfsfromnb os.nb imgfs.bin
imgfstodump imgfs.bin
imgfsfromdump imgfs.bin imgfs-new.bin
imgfstonb imgfs-new.bin os.nb os.nb.new
step 3rd. rename os.nb.new as cg33.smg and then use ezxcodec to repack sbf."

And you must have based rom - some european or oder because when you split file the crc must be the same .